RSES Condenser Systems 3 — Questions and Answers
Question 1: When a technician observes a high condenser approach temperature on a water-cooled unit, what is the most likely cause?
- Low refrigerant charge
- Fouled condenser tubes or inadequate water flow (Correct answer)
- Overcharged system
- Low ambient temperature
Correct answer: Fouled condenser tubes or inadequate water flow
Fouled tubes or restricted water flow reduce heat transfer, causing the condensing temperature to rise well above the leaving water temperature.
Question 2: What is the correct sequence for purging non-condensable gases from a condenser?
- Run system to high head pressure, then vent from highest point (Correct answer)
- Recover refrigerant, pressurize with nitrogen, then vent
- Shut off compressor, open liquid line valve, vent from service port
- Add refrigerant until pressure drops, then vent condenser
Correct answer: Run system to high head pressure, then vent from highest point
Non-condensables migrate to the top of the condenser; with the system running, venting slowly from the highest point releases trapped gases while minimizing refrigerant loss.
Question 3: A flooded condenser control valve modulates to:
- Maintain constant suction pressure
- Flood the condenser with liquid to raise head pressure in cold weather (Correct answer)
- Reduce refrigerant charge during high ambient conditions
- Control condenser fan speed
Correct answer: Flood the condenser with liquid to raise head pressure in cold weather
In cold ambient conditions, a flooded condenser control valve backs liquid refrigerant into the condenser to reduce effective surface area and maintain adequate head pressure.
Question 4: Which measurement best confirms adequate airflow through an air-cooled condenser?
- Refrigerant subcooling level
- Static pressure drop across the coil (Correct answer)
- Compressor discharge temperature
- Suction superheat
Correct answer: Static pressure drop across the coil
Measuring static pressure drop across the condenser coil indicates whether airflow is within the design range for that coil.
Question 5: In an evaporative condenser, Legionella risk is primarily controlled by:
- Maintaining refrigerant subcooling above 10°F
- Proper biocide treatment and water management program (Correct answer)
- Keeping sump water below 50°F
- Installing UV lights on the condenser coil
Correct answer: Proper biocide treatment and water management program
Legionella thrives in warm stagnant water, so a proper biocide treatment and water management plan is the primary control measure in evaporative condensers.
Question 6: What is the effect of increased condenser water flow rate beyond design on a water-cooled condenser?
- Significant improvement in condensing temperature
- Diminishing returns with potential erosion of tube walls (Correct answer)
- Higher condensing pressure
- Increased subcooling only
Correct answer: Diminishing returns with potential erosion of tube walls
Beyond design flow, the benefit to condensing temperature diminishes while the increased velocity risks erosion-corrosion of tube walls.
Question 7: Subcooling in a condenser is measured as:
- Saturated condensing temperature minus liquid line temperature (Correct answer)
- Discharge temperature minus saturated condensing temperature
- Liquid line temperature minus suction temperature
- Condensing temperature minus ambient temperature
Correct answer: Saturated condensing temperature minus liquid line temperature
Subcooling is the difference between the saturated condensing temperature (at head pressure) and the actual liquid refrigerant temperature leaving the condenser.
RSES Condenser Systems 3
When a technician observes a high condenser approach temperature on a water-cooled unit, what is the most likely cause?